(1) Field of the Invention
The present invention relates to an aircraft fitted with at least one fuselage sponson.
(2) Description of Related Art
As shown in Documents U.S. Pat. No. 2,448,075 or GB 2 342 635, such a fuselage sponson is generally arranged longitudinally on a side flank of a main body of a fuselage. This type of sponson also serves to increase the buoyancy of the aircraft, e.g. for a seaplane, or indeed more generally for housing and protecting equipment of an aircraft.
By way of example, aircraft equipment protected in this way by a sponson may comprise rear landing gear, buoyancy systems, in particular inflatable systems, position or lighting lamps, and/or fuel tanks for feeding at least one engine of the aircraft with fuel.
Furthermore, such a sponson may also be used as a step, and it is consequently designed to enable a person to climb onto it, e.g. to facilitate maintenance of the aircraft.
Finally, a fuselage sponson also presents dimensional and shape characteristics that seek to optimize the aerodynamics of the aircraft, and in particular to limit the aerodynamic impact of the sponson. Sponson shapes are thus adapted to limit the increase in the aerodynamic drag coefficient caused by such a projection emerging from the main body of the fuselage, particularly since the surface area presented by the sponson for friction with air also generates an increase in drag.
In general manner, aircraft fitted with such fuselage sponsons may also have sliding side doors that are movable in translation so as to be opened, generally by being moved towards the rear along the main body of the fuselage. Under such circumstances, it can happen that there is interference between the sliding door and the fuselage sponson arranged longitudinally on a flank of the aircraft.
In order to mitigate that interference between the sponson and the sliding door, various solutions have been envisaged.
A first solution consists in making an opening in the bottom portion of the sliding door so as to avoid interference with the sponson when opening the door. In certain applications, that opening can then be covered with a flap portion of the door suitable for moving downwards and being pivotally mounted about an axis that is substantially horizontal. Such a flap portion of the door is thus distinct from a sliding portion of the door. An example of such a door with an opening is described in particular in Document U.S. Pat. No. 6,189,833.
Such a first solution to the problem of interference is nevertheless below optimum in terms of noise and temperature comfort for the occupants of the aircraft. Specifically, with a downwardly movable flap portion for the bottom of the door it is not possible to guarantee that the cabin is closed, at least when the opening in the bottom portion is not covered. Noise nuisance and temperature discomfort can then penetrate through that type of door with an opening in its bottom portion.
A second solution that has already been envisaged consists in making a notch in the sponson so as to allow the sliding door to pass freely between the main body of the fuselage and a portion of the sponson.
Under such circumstances, such a notch may present various shapes corresponding to various embodiments of this second solution. Thus, in one embodiment, the notch may extend vertically over the full height of the sponson.
Nevertheless, that embodiment is problematic since it leads to a large increase in aerodynamic drag for the aircraft. It therefore does not guarantee good aerodynamic characteristics for such a fuselage sponson.
In another embodiment, and by analogy, the notch may extend horizontally over the entire length of the sponson.
While the aircraft is in movement, a large amount of turbulence can then form in the air stream that is deflected by the sponson. Such turbulence is also highly problematic since it can interact dangerously with aerodynamic members at the rear of the aircraft. By way of example, such rear members may be formed by wings or ailerons, stabilizer surfaces, horizontal or vertical stabilizers, or blades of a tail rotor in the particular circumstance of a rotorcraft. Under certain circumstances, such an embodiment can thus lead to large losses of efficiency from the aerodynamic members at the rear of the aircraft, and it can thus be harmful to the aerodynamic characteristics of the aircraft and can affect the performance of the aircraft.
Finally, a last known solution consists in causing the sliding door to open longitudinally towards the front of the aircraft, or in other words in a direction going away from the sponson.
Although such an embodiment appears to satisfy aerodynamic and acoustic comfort constraints, it is nevertheless not compatible with all aircraft architectures. Specifically, certain aircraft do not have sufficient length to enable a sliding door to open forwards in that way. This applies in particular to aircraft that present a front door immediately in front of the sliding door for giving access to a cockpit of the aircraft.